Characteristics of Old-Growth Douglas Firs

Old-growth Douglas-fir (Pseudotsuga menziesii) trees are a significant though minor component of most old-growth redwood (Sequoia sempervirens) forests in the Santa Cruz Mountains, sharing the canopy with redwoods. Unlike redwood, they succumb readily to such tree-damaging agents as disease, insects, windfall, and wildfire. In the Santa Cruz Mountains they are very susceptible to a heart rot fungus not found further north and thus seldom live more than 350 years. Consequently Douglas-firs are the major source of recruitment for large snags and large down logs in redwood-Douglas-fir stands. They also assume old-growth characteristics at a much earlier age than redwood, at about 175 years.

The softer heartwood of old-growth Douglas-fir is the primary resource used by our three species of cavity-excavating woodpeckers and it typically provides the majority of tree cavities in younger old-growth stands. These cavities are used by small mammals for denning, bats for roosting, and are required for nesting by 12 species of forest birds. Thus old-growth Douglas-firs are critically important in sustaining wildlife habitat in our redwood – Douglas-fir forests.

Identifying Characteristics of Old-growth Douglas fir Trees in the Santa Cruz Mountains not all need be present

Outline of the live crown is irregular

Tree top is dead, damaged, or broken

Epicormic branching* or reiterations** are present

Large horizontal branches (>8") are present in the upper half of the tree

Cavities, hollows, broken limbs or other "defect" is present

Burn scars are present on the trunk

Bark is thick, loose, and "punky" to the touch

- prepared by S. Singer, forest biologist, October 2009

_______* Multiple very small branches arising from the same point on the trunk.** A tree-like branch growing from a dormant bud in the trunk or in a large limb.

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